1. Field of the Invention
The present invention relates to a vessel and apparatus for concurrently carrying out reactions and separating the reactants from products by fractional distillation.
2. Related Art
Recently a new method of carrying out catalytic reactions has been developed, wherein the components of the reaction mixture are concurrently separable by fractional distillation. Several systems have been proposed and one commercially successful uses the catalyst as the catalytic distillation structure. Such a system is variously described in U.S. Pat. Nos. 4,215,011; 4,232,177; 4,242,530; 4,250,052; 4,302,356; 4,307,254; 4,336,407; 4,439,350; 4,443,559; and 4,48,775 commonly assigned herewith.
Briefly, the commercial structure described therein comprises a cloth belt with a plurality of pockets spaced along the belt and containing particulate catalyst material. The cloth belt with catalyst filled pockets is wound into a helix about a spacing material such as knitted stainless steel wire mesh, and these "bales" loaded into a distillation column. Additionally, the above cited U.S. Pat. Nos. 4,443,559 and 4,250,052 disclose a variety of catalyst structures for this use. The present invention dispenses with the belts and the bales disclosed therein.
Placing the particulate catalyst loose on standard distillation trays has also been proposed. See, for example, U.S. Pat. No. 4,215,011 and U.K. patent GB 2,096,603 A. The placement of the catalyst in the downcomers of standard distillation columns has been proposed as in U.S. Pat. No. 3,634,535. Fluidization of the catalyst on the trays by the action of the vapor passing through the tray has also been suggested as in U.S. Pat. No. 4,471,154, wherein a fluidized height of the bed is determined, at least in part by the volume of the bed defined by the tray containing the catalyst and a screen, i.e., about 2 to 10 times the height of the settled catalyst bed. Some deficiencies of such fluidized beds were recognized in Chemiker-Zeitung/Chemische Apparatur, vol. 90, no. 13, July 1966 and U.S. Pat. No. 4,215,011. One object of the present invention is to minimize catalyst movement to prevent attrition, so "fluidization" is kept to the minimum.
Since most reactions occur in the liquid phase and vapor flow through the catalyst on trays causes problems such as increased pressure drop and catalyst attrition, vapor by-passes around the catalyst containing trays have been proposed. See for example U.S. Pat Nos. 4,847,430 and 4,847,431. Disclosed therein are alternating catalyst containing trays and standard distillation trays with the vapor from the distillation trays bypassing the catalyst containing trays and passing directly to the next higher distillation tray (U.S. Pat. No. 4,089,752 discloses the by-pass in a non-catalytic reaction distillation system).
In most applications the reaction being carried out is exothermic with the heat of reaction causing partial vaporization of the reaction mixture. The present invention retains the benefits of catalytic distillation (e.g. exothermic heat utilization), but avoids the catalyst bag distillation structures on the one hand and the fluidized bed on the other hand.